This invention relates to improvements in a device for controlling a quantity of lubricating oil in an automatic transmission for a vehicle, wherein a pump is rotated to circulate the lubricating oil.
The circulation quantity of lubricating oil (herein, the circulation quantity has the same meaning as the lubricating oil quantity or the lubricating oil pressure, etc.) in an automatic transmission has heretofore been mechanically determined by the rotary speed of a pump and the engine load (based upon, e.g., a throttle opening). The rotary speed of the pump directly corresponds to the engine rotary speed at a ratio of 1:1. When the pump rotary speed increases to a predetermined value or more, the circulation quantity is determined in association with the engine load represented by the throttle opening or the like. When the pump rotary speed is low, the circulation quantity is determined by a discharge value of the pump.
However, the circulation quantity of lubricating oil is not necessarily optimally defined by these factors. For example, during coasting at high speed, the engine load is negative (throttle opening is zero), however, the automatic transmission members rotate at high speed due to the reverse driving torque. Consequently, a considerable quantity of the lubricating oil is needed.
To obviate the above-described disadvantage, for example, Japanese Patent Kokai (Laid-Open) No. 86749/1984 discloses a device for supplying lubricating oil. Even when the throttle opening is low, and hence the line pressure is lower than a predetermined regulated pressure value of a torque converter oil pressure control valve (a secondary regulator valve), a sufficient quantity of oil can be supplied to lubrication section without lowering the torque converter oil pressure. However, such lubrication supply devices are designed to obviate the disadvantageous relationship between the torque converter and throttle opening at times of low throttle openings. Such devices, however, do not optimize the lubricating oil quantities at all times.
Namely, the prior art (including Patent Kokai (Laid-Open) No. 86749/1984), has a constant quantity of lubricating oil when the throttle opening zero, so that, the quantity of lubricating oil is not increased or decreased as occasion demands at the time of a zero throttle opening. As a consequence, the quantity of lubricating oil becomes insufficient when coasting at high speed for a long period of time, and the like.